Subject: CVE-2024-49983: ext4: drop ppath from ext4_ext_replay_update_ex() to avoid double-free

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

ext4: drop ppath from ext4_ext_replay_update_ex() to avoid double-free

When calling ext4_force_split_extent_at() in ext4_ext_replay_update_ex(),
the 'ppath' is updated but it is the 'path' that is freed, thus potentially
triggering a double-free in the following process:

ext4_ext_replay_update_ex
  ppath = path
  ext4_force_split_extent_at(&ppath)
    ext4_split_extent_at
      ext4_ext_insert_extent
        ext4_ext_create_new_leaf
          ext4_ext_grow_indepth
            ext4_find_extent
              if (depth > path[0].p_maxdepth)
                kfree(path)                 ---> path First freed
                *orig_path = path = NULL    ---> null ppath
  kfree(path)                               ---> path double-free !!!

So drop the unnecessary ppath and use path directly to avoid this problem.
And use ext4_find_extent() directly to update path, avoiding unnecessary
memory allocation and freeing. Also, propagate the error returned by
ext4_find_extent() instead of using strange error codes.

The Linux kernel CVE team has assigned CVE-2024-49983 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 5.10.227 with commit 8c26d9e53e5f
	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 5.15.168 with commit a34bed978364
	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 6.1.113 with commit 6367d3f04c69
	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 6.6.55 with commit 1b558006d98b
	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 6.10.14 with commit 3ff710662e8d
	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 6.11.3 with commit 63adc9016917
	Issue introduced in 5.10 with commit 8016e29f4362 and fixed in 6.12-rc1 with commit 5c0f4cc84d3a

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-49983
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	fs/ext4/extents.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/8c26d9e53e5fbacda0732a577e97c5a5b7882aaf
	https://git.kernel.org/stable/c/a34bed978364114390162c27e50fca50791c568d
	https://git.kernel.org/stable/c/6367d3f04c69e2b8770b8137bd800e0784b0abbc
	https://git.kernel.org/stable/c/1b558006d98b7b0b730027be0ee98973dd10ee0d
	https://git.kernel.org/stable/c/3ff710662e8d86a63a39b334e9ca0cb10e5c14b0
	https://git.kernel.org/stable/c/63adc9016917e6970fb0104ee5fd6770f02b2d80
	https://git.kernel.org/stable/c/5c0f4cc84d3a601c99bc5e6e6eb1cbda542cce95